Method and apparatus for sealing capillary tubes



an. 16, 1951 oc 2,538,571

METHOD AND APPARATUS FOR SEALING CAPILLARY TUBES Filed April 9, 1949 I N VEN TOR.

RUDOLF KOCH A TTORNE Y.

Patented Jan. 16, 1951 1 METHOD AND AFPARATUS FOR SEALING CAPILLARY TUBES Rudolf Koch, Milwaukee, Wis., assignor to Automatic Products Company, Milwaukee, Wis., a corporation of Wisconsin ApplicationApril 9, 1949, Serial No. 86,451

This invention relates to a method and apparatus for burning off or hermetically sealing a capillary tube.

The sealing of copper and other metallic 7 Claimsi (Cl. 219-4) the tube will be substantially vertical when contacting the outer portion of the wall of each hole, as illustrated in Fig. 3. The holes could, however, be coaxial' since the usual capillary capillary charging tubes has heretofore been a 55: tube is readily bent as desired. The vertical distedious and expensive process. The conventance between the pinch-off tools is sufficient to tional practice has been to crimp the tube after permit pliers to be inserted between the pinchthe. system has been charged to form a temoff tools to flatten the capillary tube for a purporary seal. Fluxis then applied to the end pose which will be explained hereinafter. of the tube and the tube soldered. In addition A reciprocable plunger 48 is mounted within to being a process involving a lot of handling the casing 42 of each crimping tool and has a and requiring great care, the results obtained nose 44 adapted to bear against the wall of the were" often unsatisfactory due to minute leaks. capillary tube. The plunger 4!! is biased out- The principal object of this invention is to wardly by means of spring lfi'bearing against provide apparatus for rapidly sealing capillary shoulder 48 on the plunger and is guided bypin tubes. .7 59 projecting through slot 52 in the outer end Another object is to provide apparatus for of the plunger to maintain the nose in a versealing capillary tubes in a simple manner while tical position. Rotation of the manually operconsistently obtaining a high quality of work. ated handles 54 about pin 56 will cause cam 7 Another object 'is to provide a process for surface 58 to bear against the end of the plunger greatly simplifying the method and reducing the to force the plunger into engagement with the cost of sealing capillary tubes. wall of the capillary tube to collapse or crimp Still another object is to provide a new process the tube. Crimping in this manner serves both for closing off capillary tubes. 7 to seal the fluid in the system from the heat Other objects and advantages will be'pointed' of the welding operation and to establish good out in, or be apparent. from, the specification electrical contact with the tube. and claims, as will obvious modifications of the Sealing or burning off the capillary tube with single embodiment of the apparatus shown in this apparatus is a simple, rapid process. After the drawings, in whichz i the particular system has been charged, the Fig. 1 is a top plan view of the apparatus to capillary tube maybe crimped to form a tememployed in this invention; porary seal. The endof the tube is inserted Fig. 2 is a front elevation of Fig. 1 with parts through each of the holes 36, 38 in crimping tools broken away; and ID, l2. The lower handle 54 is then rotated in Figs. '3, 4, 5 and 6 illustrate the operation of the direction indicated by the arrow to crimp this apparatus and the steps employed in the tube 60 as indicated in Fig. 4. Pliers are now process for burning off the capillary tube. utilized to flatten the tube between the pinch-off Referring to the drawings in detail, two vertools (Fig. 4) and the upper crimping tool is tically staggered crimping tools l0, [2 are operated. When switch 34 is closed to complete mounted in blocks l4, l6, respectivelymounted the circuit (Fig. 5) the tube is melted between on and insulated from base plate 18 by means 40 the pinch-off tools, as indicated in Fig. 6, and of insulating blocks 20, 22. Plate l8 in turn the melted tube ends 62, 62 are Welded. About may be mounted on a suitable work bench 24 500 amperes at 6 volts has proven highly sucwhich may be provided with a convenient reccessful in obtaining a clean, rapid weld. tangular cut 26 permitting access to the under- The simplicity of this method will be appreside of the lower crimping tool l2. Bus bars ciated when compared to the tedious processes 28, 30, in circuit with the secondary of stepheretofore employed. The weld thus obtained down transformer 32 and a foot or hand operis uniform and of very high quality, while ated switch 34, are connected to blocks i4, i6, former processes frequently failed to seal the respectively. Therefore, with the use of metallic system. Experimentation has indicated that in blocks and crimping tools the circuit may be most cases it is desirable to flatten the tube be closed when the gap between the tools is bridged. tween the pinch-off tools by means of pliers or As is clear in the drawings, the vertically other mechanism as indicated in Fig. 4 in order spaced crimping tools are provided with holes to obtain a seal of uniform high quality since 36, 38 adapted to receive a capillary tube and the gases in the tube expand and cause the weld having their centers horizontally displaced so to blow out. When working with tubing having a very small inside diameter, however, satisfactory results may sometimes be obtained without flattening the tube prior to welding.

Although but one embodiment of the present invention has been illustrated and described, it will be apparent to those skilled in the art that various changes and modifications, may be made therein without departing from the spirit of the invention or from the scope of the appended claims.

I claim:

1. The method of hermetically sealing a capillary tube, comprising the steps of, collapsing a portion of the Wall of said tube until juxtaposed interior surfaces are in contact, establishing electrical contact at axially spaced positions on either side of said portion, and passing an electric current between said positions to melt said portion.

2. The method of hermetically sealing a capillary tube, comprising the steps of, crimping said tube at two axially spaced points, and passing an electric current between said points to melt and weld the tube.

3. The method of hermetically sealing a capil' lary tube, comprising the steps of, collapsing a portion of the wall of the tube until juxtaposed interior surfaces are in contact, crimping the tube at axially spaced points on each side of the collapsed portion, and passing an electric current between said points to melt said collapsed portion.

4. Apparatus for hermetically sealing a, capillary tube comprising, spaced crimping tools adapted, to, receive a capillary tube and crimp the tube at spaced points, an electric circuit conmeeting said crimping tools to a source of elec tric potential and including a switch, said switch being operable when closed to permit passage of electric current through the tube between said points to melt the tube between said points, the melted metal coalescing to seal the end of each section of the capillary tube so melted.

5. A device for hermetically sealing a capillary tube having a portion of the tube Wall collapsed to bring juxtaposed interior surfaces into con.- tact comprising, an electric circuit including a current source, means for establishing electric contact with said tube on each side of said collapsed portion, means for temporarily sealing said tube on each side of said collapsed portion,

4 and switch means included in said circuit for permitting current flow through said tube between said electric contacts to melt the tube at said collapsed portion when the switch is closed.

6. A device for sealing capillary tubes, comprising, a pair of crimping tools, an aperture in each of said tools, said apertures being generally axially alignedand being adapted to receive a capillary tube, means associated with each of said tools to crimp a portion of the capillary tube passing through the corresponding hole, circuit means for connecting said tools with a source of electrical energy so current may be passed through said tube between the crimped portions, said circuit means including a switch.

7. A device for sealing capillary tubes, comprising, a pair of crimping tools each of which include a hole and a generally reciprocal plunger, said holes being generally aligned so a tube may be passed through both holes, each of said plungers being generally diametrically movable into. and out of their corresponding holes and being adapted to abut and crimp a tube passing through the hole, means for reciprocating said plungers in said tools, circuit means for connecting said plungers to, a source of electrical energy and including a switch, for completing the circuit to. pass current through the tube between the tools.

RUDOLF KOCH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,259,271 Murray 1 Mar. 12, 1918 1,296,780 Dyer Mar. 11, 1919 1,339,417 Pierce May 11, 1920 2,056,398 Herzog Oct. 6, 1936 2,057,969 Payson et a1 Oct. 2.0, 1936 2,132,071 Johnson Oct. 4, 1938 2,174,906 'Wagner Oct. 3, 1939 2,202,580 Hahn May 28, 1940 2,264,817, Uhler Dec. 21, 1941 FOREIGN PATENTS Number Country Date 490,586 Great Britain Aug. 17, 1938 

